Removal of pharmaceuticals by a potassium ferrate( vi ) material: from practical implementation to reactivity prediction

This study investigated the degradation of metoprolol (MET), carbamazepine (CBZ), ciprofloxacin (CIP) and hydroxy-ibuprofen (OH-IBU) in aqueous solution by a ferrate( vi ) material obtained by dry synthesis according to patent WO2008065279. Ferrate( vi ) had the highest reactivity with CIP, with a second-order rate constant of 89 ± 2 M −1 s −1 at pH 10.3 ± 0.3. The rate constants of ferrate( vi ) with MET and CBZ under the same conditions were 3.7 ± 0.3 M −1 s −1 and 13.1 ± 0.8 M −1 s −1 , respectively, while no reaction took place with OH-IBU. We also evaluated the removal efficiencies of nine selected pharmaceuticals, including MET, CBZ, CIP and OH-IBU, detected in a real hospital wastewater (HWW) with concentrations ranging from 73 ± 4 ng L −1 to 159 ± 8 μg L −1 by applying Fe( vi ) technology. The abatement of the targeted pharmaceuticals depends on their structures. Because Fe( vi ) captures electrons during the oxidation process, we proposed to correlate the reactivity of Fe( vi ) with the first ionization potential (IP) of the pharmaceuticals. The first IP values of MET, CBZ, CIP, OH-IBU and diclofenac (DFC) were determined by gas-phase UV photoelectron spectroscopy (UV-PES). The UV-PES data were also interpreted using density functional theory (DFT) calculations.